Question

Protozoa in activated sludge primarily contribute to

• A. Methane formation
• B. Nitrogen fixation
• C. Predation of dispersed bacteria and floc formation
• D. Sulphur oxidation

Hint:

Role of protozoa in activated sludge: \[ \boxed{ \begin{aligned} &\text{Feed on free bacteria}\\ &\text{Improve effluent quality}\\ &\text{Promote floc formation} \end{aligned} } \]

Answer 1

The Correct Option is C

Step 1: Picture the activated sludge community.
Activated sludge is not just bacteria. It also hosts protozoa that graze on the bacterial population living in the mixed liquor.
Step 2: Think about what that grazing achieves.
By feeding on free swimming, dispersed bacteria, protozoa reduce the number of loose cells and help clarify the water leaving the aeration tank.
Step 3: Connect grazing to floc quality.
This predation also encourages the remaining bacteria to clump together into denser, better settling flocs, improving overall treatment performance.
\[ \boxed{\text{Predation of dispersed bacteria and floc formation}} \]